Extended Data Fig. 5: U2 snRNP SF3 phosphorylatable motifs are conserved and surface-accessible.
From: Polyamine-dependent metabolic shielding regulates alternative splicing
a, Violin plot representation of the isoelectric points of significantly altered phosphopeptides in DU145 cells upon polyamine deprivation (SAM486A 1 µM + DFMO 50 µM, 48 h). White circles show the medians; box limits indicate the 25th and 75th percentiles; whiskers extend 1.5 times the interquartile range from the 25th and 75th percentiles and polygons represent density estimates of data and extend to extreme values. b, z-scored heat map of phosphosites that are upregulated upon polyamine deprivation (SAM486A 1 µM + DFMO 50 µM, 48 h) and their reversibility following supplementation with exogenous polyamines (putrescine, spermidine, and spermine; 10 µM for 48 h). c, Schematic representation of the conservation across species of the main altered phosphosites upon PA deprivation in SF3A1, SF3A3 and SF3B2. Arrows highlight the position of phosphorylated serines (S) or threonines (T) altered upon PA deprivation. d, Schematic model representing the impact of PA deprivation in the phosphorylation of SFs and the subsequent perturbation on pre-mRNAs alternative splicing. Created in BioRender. Biorender1, A. (2025) https://BioRender.com/zitthjc. e, Phosphorylation levels of SF3A3 at Ser365, Ser367, Ser369 and Thr475 in DU145 cells upon polyamine deprivation (SAM486A 1 µM + DFMO 50 µM, 48 h) and following supplementation with exogenous polyamines (putrescine, spermidine, and spermine; 10 µM for 48 h). Abbreviations: S: SAM486A, D: DFMO, PA: polyamines, S:Serine, T:threonine. Statistics: Two-tailed Mann-Whitney U-test is applied in (a). p: p-value.
